Thanks for the query to H.C.M. Forum.
May be due to ,
as you are complaining that this happens after or during exercise , so reason may be exercise tension and anxiety.
2 Over exertion may be the next reason
3 Least possibility may be due to asthma
. Diagnosis can be confirmed by Pco2 & po2 & pulmonary function test.
In my opinion get in blood for hemoglobin
level , if it comes
Good luck. Dr. HET